API for Callback Functions for Network and WtNetwork Structures

Overview

Types of storage and types of term

The callback API provides a way for a Network structure to signal precisely when a particular change (e.g., an edge toggle) is about to take place. It is intended to simplify and robustify the management of u_ functions from the Terms API.

Formal API definition

New types

void OnNetworkEdgeChange(Vertex, Vertex, void *, Network *) and void OnWtNetworkEdgeChange(Vertex, Vertex, double, void *, Network *), a callback function, compatible with u_ functions and Mu_ functions both (since a void* can be any pointer).

New struct elements

Network and WtNetwork

OnNetworkEdgeChange **on_edge_change and OnWtNetworkEdgeChange **on_edge_change: an array of pointers to callback functions.

void **on_edge_change_payload: an array of void pointers that get passed as the third argument to the corresponding on_edge_change function.

unsigned int n_on_edge_change: number of callbacks in the above two arrays.

unsigned int max_on_edge_change: the amount of space allocated for the above two arrays.

New functions

void AddOnNetworkEdgeChange(Network *nwp, OnNetworkEdgeChange u_func, void *payload, unsigned int pos) and void AddOnWtNetworkEdgeChange(WtNetwork *nwp, OnWtNetworkEdgeChange u_func, void *payload, unsigned int pos): Set a callback u_func to be called with argument payload whenever an edge in nwp is changed. Its position in the list (i.e., the order in which it is called) is set to be pos (with large pos truncated to indicate the last position).

void DeleteOnNetworkEdgeChange(Network *nwp, OnNetworkEdgeChange u_func, void *payload) and void DeleteOnWtNetworkEdgeChange(WtNetwork *nwp, OnWTNetworkEdgeChange u_func, void *payload): Search the list of nwp’s callbacks for u_func and payload and delete the callback when it is found. (If it is not found, an immediate error is raised.)